Apparatus and method for sensing slippage of elevator drive cable over a traction sheave

ABSTRACT

An elevator includes an evaluation unit. A pair of position pick-ups are connected to the cable assembly and/or driving pulley of the elevator and coupled to the input of the evaluation unit. The elevator is accelerated or decelerated for checking adhesion of the cable onto the driving pulley (traction sheave). The motion parameters of the cable assembly and the driving pulley are sensed separately, and the drive capability can be determined therefrom.

This invention relates to an apparatus for sensing physicalcharacteristics, in particular motion parameters, of a freight and/orload elevator, with the elevator comprising at least one cable assemblywhich is guided over a driving pulley and whose one end has suspendedtherefrom the elevator car and whose other end a counterweight, and saidelevator being driven by a drive motor which is controlled by anelectric control circuit and acts on the driving pulley, and including abraking device which is connected to the driving pulley and controlledby the control circuit.

Safety tests which are performed with freight and passenger elevatorsform the background of the present invention. Elevators of this typemust be controlled at regular intervals, and characteristics such aspaths of travel, braking paths, catch paths and non-slippage (drivecapability) of the cable assembly, which is driven by the drivingpulley, have to be determined.

The checking of elevators has so far involved a lot of work because thetesting of the function of the brake and the catch device required theloading of the elevator with the admissible useful load or even with 1.5times the useful load when the non-slippage property was checked. Theloading and unloading operations in connection with the necessaryweights are not only time-consuming, but also call for great physicalefforts. Moreover, the weight test for the elevator system greatlystresses the loaded components.

U.S. Pat. No. 3,781,901 discloses an apparatus for displaying andstoring an elevator movement. The rotation of the driving pulley of theelevator is sensed by a sensor and plotted on a time-path diagram forobserving the elevator movement. The elevator movement is thereby to beoptimized if necessary. DE-A-3822488 discloses a method for controllingposition and movement of a cable-moved transportation means so as todetermine cable slippage and stretching properties of the carryingcables during operation. The signals that are evaluated for determiningthe position are directly obtained in an optoelectronic way from theexisting form of the cabled elements moving the transportation means.

In the two above-mentioned documents the checking of elevators is not atall possible or can only be carried out under great efforts.

It is the object of the present invention to provide means which areused for checking freight/and or passenger elevators and with the aid ofwhich the amount of work spent on the test method is considerablyreduced while the test quality is increased at the same time.

In accordance with the invention, this object is attained in that thereis provided an evaluation unit with a timer, as well as a positionpick-up which communicates with the cable assembly and/or the drivingpulley and is connected to an input of the evaluation unit, and in thatthe evaluation unit comprises other inputs which are connectable toswitching points of the control unit at which signals are present forcontrolling the sequence of motions of the elevator.

Kinematic elevator data, i.e. travel path values and the associated timemeasurement values, can be determined with such an apparatus in responseto the signals that control the sequence of motions of the elevator, andthe necessary test characteristics can be found on the basis of thekinematic data. As far as safety aspects are concerned, the test methodof the invention is a considerably improvement as there are no heavyloads acting on the elevator during testing.

In particular, the evaluation unit advantaeously includes a means fordetermining and recording distance, speed and acceleration values as afunction of time and path. The recorded braking and catch curves aredisplayed on a screen or printed out by a printer and superimposed withcalculated envelopes (which set admissible upper and lower limits). Theeffectiveness of the brake and the catch device can thus be determinedin an easy way. The determined curves may be stored on a data carrier.The evaluation means expediently comprises a computer, preferably apersonal computer.

In another expedient embodiment the apparatus of the invention comprisesa force sensing element which is connected to the cable assembly andwith the aid of which the forces that are transmitted by the cableassembly and determine the sequence of motions of the elevator car canbe determined. Especially the non-slippage property of the cableassembly, which is driven by the driving pulley, can advantageously bechecked by means of such a force measurement.

An advantageous development of the invention consists in a method forsensing physical characteristics. The cable, the elevator car and thecounterweight are specifically accelerated or decelerated during normaltravel operation for checking the adhesion of the cable to the drivingpulley. The motion parameters of the cable and the driving pulley arehere sensed separately in dependence upon time.

It is of advantage when the motion parameters of cable and drivingpulley are additionally compared with a given motional limit parameter(e.g. a limit curve). When the limit value is exceeded, the drivecapability of the driving pulley is ensured at any rate.

An advantageous development also exists when, in the case of differentmotion parameters of cable and driving pulley, the drive capability ofthe driving pulley is determined on the basis of the differencemeasured.

Other expedient embodiments of the invention will become apparent fromthe subclaims.

The invention shall now be explained and described in more detail withreference to the embodiments and the attached drawings, in which:

FIG. 1 (schematically) shows an elevator system wherein the apparatus ofthe invention is used for checking purposes;

FIG. 2 is a schematic representation of an embodiment of an apparatus ofthe invention;

FIG. 3 is a front view of an embodiment regarding a position pick-upusable in an apparatus of the invention;

FIG. 4 is a side view of the position pick-up according to FIG. 3;

FIG. 5 shows time diagrams of the measuring signals that are output bythe position pick-up according to FIGS. 3 and 4;

FIG. 6 shows an evaluation circuit for evaluating the measuring signalsoutput by the position pick-up according to FIGS. 3 and 4, 7, 8, 9 and11, respectively;

FIG. 7 shows an embodiment of a force sensing element usable in anapparatus of the invention;

FIG. 8 shows a position pick-up used in the force sensing element ofFIG. 7 as a transducer.

FIG. 9 shows another embodiment of a force sensing element usable in anapparatus of the invention;

FIG. 10 shows another embodiment of a force sensor with dial gauge foruse in an apparatus of the invention;

FIG. 11 shows a position pick-up (dial gauge) which can be used in theforce sensor of FIG. 10 as a transducer;

FIG. 12 shows an embodiment of a position pick-up used in an apparatusof the invention in the form of a double-type pick-up;

FIG. 13 is a catch diagram with the actually recorded function f independence upon path (s) over time (t); and

FIG. 14 is a catch diagram with catch curve f of FIG. 13 and withenvelopes h serving as limit values for the catch curve.

An elevator system which is to be checked by the apparatus of theinvention shall first of all be described so that it will be more easyto explain the function of the inventive apparatus further down in thetext.

In FIG. 1 reference numeral 1 designates a driving pulley whichcomprises two guide grooves for a cable assembly 2, which is formed bytwo cables in the present case. An elevator car 3 is secured to one endof cable assembly 2. A counterweight 4 is suspended at the other end ofcable assembly 2. The mass of counterweight 4 generally corresponds tothe mass of elevator car 3 plus half the admissible car load. 5designates a motor-gearing-brake unit for the drive of driving pulley 1.This unit includes a hand wheel 10 for rotating driving pulley 1. Unit 5includes a brake for driving pulley 1. Unit 5, including driving pulley1, is located above a ceiling 11 closing the elevator shaft upwards.

During travel elevator car 3 is moved via cable assembly 2, which isdriven by the motor-gearing-brake unit via driving pulley 1. It isnecessary for a perfect operation of the elevator system that the cableassembly be placed relative to the driving pulley in a sufficientlynon-slipping way. The elevator car can also be moved by hand wheel 10 incase of need, or during repair or checking operations.

In FIG. 2 reference numeral 8 designates an evaluation unit whichincludes a personal computer 12, an input/output interface 13 and aninterface module 14 in the present embodiment. The broken border line 6'is to indicate that the input/output interface 13 and the interfacemodule 14 form a functional unit. As a rule, the personal computerincludes a screen 38 as a display device as well as an entry keyboard37. Data is exchanged in both directions between the individual modulesof the evaluation unit in accordance with the plotted arrows connectingthe modules. In the present embodiment evaluation unit 8 is respectivelyconnected via one of lines 15-17 to a first position pick-up 7 which maybe in motional communication with a cable of cable assembly 2, to asecond position pick-up 18 which may be in motional communication withdriving pulley 1, e.g. through contact, and to a force sensing element8, with the lines being connected to the evaluation unit via inputsprovided on the interface module. Reference numeral 9 designates linesthrough which the evaluation unit is connected to control circuit 48 ofthe elevator system. Like lines 15-17, lines 9 are connected to inputsprovided on interface module 14.

In the present embodiment lines 9 are combined to form a twelve-coreshielded cable. A test plug which is connectable to control circuit 48of the elevator system is provided at one end of the shielded cable anda circuit board connector with a voltage protection wiring at its otherend.

Interface module 14 comprises four subassemblies. A partial controlinterface is provided for electrical signals that are transmitted bycontrol circuit 48 via lines 9 to the evaluation unit. At each inputthis partial interface includes an optocoupler for electricallyisolating the evaluation unit from the control circuit, an operationalamplifier which is used for amplifying signals and provided with acapacitive feedback and is to be operated with one operating voltageonly, as well as a Schmitt trigger. A partial sensor interface of asubstantially symmetrical structure is provided for sensing andpreprocessing signals of the position pick-ups and the force sensingelement. As a third subassembly, the interface module 14 comprises adivider module for dividing the system clock of personal computer 12.Finally, the interface module includes an acoustic transducer whichcomprises a monoflop having a pulse width of about 500 ms and apiezoelectric bleeper arranged downstream thereof.

The input/output interface includes decoder, input/output and timermodules. The timer module includes a universally programmable counterwhose clock input is connected to the system clock of the personalcomputer via the divider module of the interface module.

FIGS. 3 and 4 are a front view and side view, respectively, of anembodiment regarding a position pick-up as may be used in an apparatusaccording to FIG. 2. The position pick-up comprises a perforated disk 19with light passage holes 20 arranged concentrically at equal distancesaround the center of rotation of the perforated disk. The perforateddisk is concentrically connected to a driving disk 21 provided with aguide slot for a driving cable of the cable assembly. The perforateddisk 19 together with driving disk 21 includes a rotary axle 24 which isrotatably supported in a holding device 23. Reference numeral 25designates a first light-barrier measuring device and reference numeral26 a second light-barrier measuring device whose light rays can exitthrough or can be interrupted by the perforated disk. The distancebetween the two light barriers and the distance between the lightpassage holes on the perforated disk are so chosen that when theperforated disk is rotated in one direction, the pulse diagrams shown inFIG. 5 are obtained with time-staggered pulses for the signals of thetwo light barrier means. The direction of rotation can be determined byevaluating the measuring signals output by the two light barriers. Acorresponding evaluation circuit is shown in FIG. 6. Apart from positionpulses whose number is characteristic of the path of travel of theelevator car, the circuit also supplies a signal indicative of themotional direction of the elevator car.

FIG. 12 shows an embodiment of a double-type position pick-up whichcombines the two pick-ups 7 and 18 in one unit. The two positionpick-ups are displaceably supported relative to each other and can thusbe pressed with the running surface 45 against the driving pulley andwith the running groove 22' against a carrying cable. The operation ofthe individual pick-ups corresponds to that of the pick-up shown inFIGS. 3 and 4.

FIG. 7 illustrates an embodiment of a force sensing element 8, which canbe used in the apparatus. The force sensing element comprises a helicalcompression spring 28 which is guided in a guide sleeve 27 and can becompressed by a pull rod 29 which at one end comprises a disk 30,against which spring 28 comes to rest, and an eye 31 at the other end.Reference numeral 32 designates a position pick-up by which adisplacement of pull rod 29 relative to guide sleeve 27 can be sensedand a measuring signal for the force acting on the pull rod can thus besupplied. The position pick-up 32 is separately shown in FIG. 8. Likethe position pick-up illustrated in FIGS. 3 and 4, it includes aperforated disk 19' and two light-barrier measuring means 25' and 26'.Perforated disk 19' is connected via a rotary axle 24' to a drivingwheel 33 which comes to rest on pull rod 29 and is driven by said pullrod.

FIG. 9 illustrates another embodiment of a force sensing element 8 whichdiffers from the embodiment shown in FIG. 7 by the provision of aposition pick-up for sensing the displacement of pull rod 29' relativeto guide sleeve 27'. This position pick-up comprises a perforated strip35 which is connected to pull rod 29' and displaceable relative to theguide sleeve and which includes light passage holes 20' arrangedequidistantly along a line. A first light barrier means 25" and a secondlight barrier means 26" are provided for scanning passage holes 20'. Theconnection of force sensing element 8 to cable 2 and its support onceiling 11 are analogous to FIG. 7.

The motional direction of the pull rod can be determined by using tworespective light barriers in the position pick-ups for the force sensingelements.

FIG. 10 illustrates another embodiment of a force sensor 8. As far asits arrangement is concerned, this sensor generally corresponds to theembodiment illustrated in FIG. 7, but differs therefrom in that theforce existing between the point of impact 34 and the elongated holes ofthe belt fastening 37 does not directly act on the spring, but isdiverted via joint 35 and presses via support balls 36 against disksprings 38. Disk springs 38 are externally guided by a sleeve 39. Thepick-up accommodating means 40 serves to accommodate the positionpick-up (dial gauge) 50 according to FIG. 11. Like the position pick-upillustrated in FIGS. 3 and 4, it comprises a perforated disk 19 and twolight-barrier measuring means 26. The perforated disk 19 is driven viathe toothed wheel 43 by the toothed rack 42. A readjusting spring servesto eliminate the play between toothed wheel 43 and toothed rack 42. Thisposition pick-up can be fixed on the clamping shaft 41 to the pick-upaccommodating means 40 of the force sensor (FIG. 10) so as to scan thespring path given by the lever ratio joint 35--support ball 36 andpick-up accommodating means 40.

Measurements regarding travel distances, speeds and accelerations of theelevator car as a function of time and of the path, respectively, independence upon the signals which control the movement of the elevatorcar and are supplied by the control circuit of the elevator system canbe carried out and recorded with the apparatus illustrated in FIG. 2 andin FIGS. 3-6 and 12. The resultant curves can be displayed on the screenof a computer or may be printed out by a printer. Statements can be madeabout the effectiveness of brake and catch device by comparison with thedesired curves.

FIG. 13 illustrates a typical course of a curve (f) with a path (s) overtime (t), as is recorded during a catch operation. This curve (f) inFIG. 13 may be shown on a screen or printed out by a printer.

FIG. 14 also shows a catch diagram with curve (f). This diagram,however, is additionally superimposed with the calculated limit curvesh, so that a statement can be made about the operativeness of the catchdevice. This diagram, too, is an original diagram as is shown on ascreen.

The braking path of the elevator car as loaded with the rated load inthe downward direction can be extrapolated from two braking pathmeasurements that are carried out one after the other (once in the emptystate upwards and once in the empty state downwards). Furthermore, thebrake deceleration in an elevator car loaded with 1.5 times the ratedload can be calculated. This is possible because these different brakingpaths (s_(empty) downwards in relation to s_(empty) upwards) are due toknown mass differences. All other masses involved (including rotaryones) take equally part in both tests and can consequently beeliminated. Speeds can also be determined because in this case, too, therespective times for the paths are stored in a table in the computer.Hence, the braking path or the brake deceleration can be calculated atany load by means of two braking tests with an empty elevator car.Hence, there is the possibility of inferring the brake characteristicsunder load from the empty elevator car. As has been described, thedeceleration under load can also be calculated. This deceleration, inturn, determines the dynamic proportion in the drive capability testwith load. Since, this deceleration can be calculated and thedecelerated masses (elevator car, counterweight) are known, the dynamicamount can also be calculated and replaced by an additionally appliedforce during testing of the drive capability without load.

The non-slippage property (drive capability) of the cable assembly canalso be determined with the aid of the above-described apparatusillustrated in FIGS. 7-11. To this end, the pull rod of the forcesensing element according to FIG. 7 or 9 or 10 must be connected to oneor several cables 2 of the cable assembly with the aid of a suitablecable clamp 49. The guide sleeve of the force sensing element isfastened via a belt band 47 and a crossbar 48 to a fixed point,expediently to ceiling 11 which closes the elevator shaft. During theslippage test the tensile force must be increased by rotating the handwheel or moving the drive until a determined limit value is reached andthe transducer produces a warning signal, or the cable or the cablesstart to slip on the driving pulley. The beginning slipping action canbe visually determined, e.g. by displacing markings made or byevaluating the signals from the first position pick-up which isconnectable to the cable assembly and from the second position pick-upwhich is connectable to the driving pulley.

The drive capability can also be determined with the above-describedapparatus in the following way:

The two position pick-ups are each in motional communication with thedriving pulley and a carrying cable. Furthermore, control line 9 isconnected to the elevator control. The movement of the elevator is nowdecelerated from full speed with a maximum braking force. From the timeof the beginning of the deceleration the position pick-ups sense thedistances covered. The latter are stored in the computer in a table withthe associated times. It can then be determined by evaluating this tablewhether and to which extent the carrying cable has slipped relative tothe driving pulley. Furthermore, it can be found out at whichdeceleration the adhesive friction has been overcome and the slippingaction has started and at which deceleration the cables have come to ahalt again relative to the driving pulley (transition from slidingfriction to adhesive friction). Since the decelerated masses (cables,elevator car and counterweight) are known or can be determined, thecorresponding forces can thus be directly extrapolated from thedecelerations. Hence, it is also possible to indicate the load whichmust at least exist so that the elevator will slip, and to indicate atwhich load an adhesive friction will again be present.

To be able to detect path differences, the two position pick-ups musteither output identical pulses for identical distances or must besynchronized with a correction factor. In each measuring operation thetwo position sensors are automatically calibrated again. This isaccomplished in the following way: At the beginning of the brakingoperation, i.e. before the brake has been applied, the elevator moves atan almost constant speed. There are no additional forces between thecarrying cable and the driving pulley. Both position sensors cover thesame distance. If the number of the pulses of both position sensors arenow related to one another, the quotient thereof is the synchronizationfactor of the two position sensors. This synchronization is e.g.accomplished through the software.

Furthermore, the above-described apparatus is capable of checking thecontrol circuit of the elevator by controlling the time sequence of thecontrol signals. It is e.g. possible to determine the time required bythe control system for disabling the drive or for applying a brake aftera safety switch has been opened.

The evaluation unit comprises a number of functional means which arepartly implemented as software. One functional means is designed todetermine the speed and/or acceleration values. The measurement of thespeed can be triggered by striking keys of the keyboard, or triggeringis effected through signals of the control circuit of the elevator.Measurement results can be displayed on the screen of a personalcomputer or may be printed out by a printer as a complete test report ifnecessary. The acoustic transducer comprised by interface module 14 maybe activated so as to draw the attention above all to inadmissible testvalues. The screen may also be used for displaying instructions for theoperation of the apparatus.

In the above-described embodiment the sensor interface causes thecomputer to interrupt its work and to update the corresponding internalmemories for path and possibly time when an external event takes place,e.g. when the perforated disk advances.

However, it is also possible to supply these pulses to aforward/rearwards counter and to display the result with the aid of aconventional display module. The corresponding forces or distances canthen be assigned to the displayed values. In the above-describedembodiment the values to be measured have been directly converted intodigital signals. Alternatively, the measurement values may also beacquired in analog form, and e.g. speeds and thus distances andaccelerations may be measured with the aid of a tachogenerator, orforces may be determined by means of strain gauges or piezoelectricpressure transducers. These analog signals can be converted by an A/Dconverter into digital signals and then further processed by anevaluation unit.

In the above-described embodiment timer and acoustic transducer havebeen accommodated with the necessary control in the sensor interface.Alternatively, it is possible to dispense with these units and to employcorresponding members in the computer where they are controlled by thesoftware. In addition, is is possible to exchange data between computerand interface module not via an input/output module of the input/outputinterface, but to resort to standard interfaces (serial or parallel) inthe computer.

The apparatus and method of the invention offer the possibility ofsensing the movement of travel of an elevator with respect to thedistance covered and the associated time in a very precise way.Accelerations and decelerations can be recorded in a very fine timeraster. When the test method is performed, it is possible to decelerateor accelerate the empty elevator car and the counterweight and to makestatements about the active forces on the basis of the motion parametersmeasured. When the forces are related with the loaded elevator, theloading condition can be inferred from the empty elevator car.

When the method is performed in practice, the empty elevator car can bebraked during the upwardly directed travel, with an operator holding aposition pick-up 7 relative to the running carrying cable prior to andduring the deceleration. The question whether or not the carrying cableslips on the driving pulley can here be answered visually by marking theposition of the carrying cable on the driving pulley with a stroke priorto deceleration.

There are now the following possibilities:

1. The deceleration measured during the braking of the elevator isgreater than or equal to a calculated limit value; the carrying cablehas here not slipped relative to the driving pulley. The adhesivefriction between the driving pulley and the carrying cable is sufficientin this case; the drive capability is ensured.

2. The deceleration measured during the braking of the elevator is belowa calculated limit value, and the carrying cable has slipped relative tothe driving pulley. The adhesive friction as well as the drivecapability are insufficient in this case.

3. The deceleration measured during the braking of the elevator is abovea calculated limit value, and the carrying cable has slipped relative tothe driving pulley. In this case the brake must be adjusted such thatthere is a softer braking action, and the test must be repeated.

4. The deceleration measured during the braking of the elevator car isbelow a calculated limit value; the carrying cable has not slippedrelative to the driving pulley. In this case the brake must be adjustedsuch that there is a harder braking action, and the test must also berepeated.

The drive capability of the driving pulley under load can thus bedetermined by varying the braking action although the test is performedwith an unloaded, moved elevator car.

In another embodiment of this method a position pick-up 7 is secured tothe carrying cable and a position pick-up of the same type isadditionally provided on the driving pulley. Hence, the movements of thedriving pulley and the cable are sensed and recorded separately independence upon time.

The empty car of the elevator is either accelerated or decelerated forchecking the drive capability. A comparison of the movements, inparticular a comparison of the two movement curves, reveals not onlywhether, but also by how much the carrying cable has slipped relative tothe driving pulley. Hence, the dynamic characteristics regarding thedrive capability under load can thus be determined by evaluating theslippage path in response to deceleration or acceleration.

This is accomplished in that e.g. the double-type position pick-upaccording to FIG. 12 is simultaneously secured to the driving pulley anda cable during the braking operation.

The elevator brake is held in the stand-by position by a braking magnetwhich is constantly connected to an electric power. When the powersupply to the braking magnet is interrupted to perform the test method,the brake becomes active. The intended interruption of the power supplyto the magnet can be used as a trigger for starting the measuringoperation.

The short period between the interruption of the power supply and thesubsequent action of the brake can be used for synchronizing theposition pick-ups for the driving pulley and the cable. A constant speedexists at both members during this short interval. The two positionsensors which are assigned to the carrying cable and the driving pulley,respectively, are synchronized during this period by comparing thenumber of counting pulses of the one position sensor with that of thesecond sensor. The resultant factor serves to convert counting pulses ofboth pick-ups into distances. Possibly existing manufacturing tolerancesbetween the two position sensors, as well as different degrees of wearare automatically eliminated.

The curves recorded by the two position sensors during the checking ofthe elevator can be compared with each other. They are congruent in thefirst portion because prior to the application of the brake the carryingcable rests on the driving pulley due to the adhesive friction. Theforce in the carrying cable increases on account of the beginningdeceleration until the point is reached at which this force overcomesthe adhesive friction and the carrying cable slips on the drivingpulley.

From this moment onwards the two recorded curves of the carrying cableand the driving pulley diverge. Moreover, the elevator car is not somuch decelerated at this moment because the threshold value of theadhesive friction has been exceeded and this energy is transformed intosliding friction. At the same time, the driving pulley is braked morestrongly because the driving force of the carrying cable which acts onthe driving pulley is reduced by the difference between adhesivefriction and sliding friction.

The test method is virtually carried out as follows:

1. The braking force of the brake is so adjusted that it is as great aspossible; it acts on the driving pulley via the gearing.

2. The empty elevator car is made to move, whereupon the brake starts tooperate after interruption of the braking magnet, and the motionparameters of driving pulley and carrying cable are recorded separately.

3. If the carrying cable has slipped relative to the driving pulley, thedrive capability is calculated and displayed by comparing the motionparameters recorded.

4. If the carrying cable has not slipped on the driving pulley, but ifthe deceleration has been above a predetermined limit value, the minimumdrive capability is calculated and displayed.

5. If the carrying cable has not slipped relative to the driving pulley,but if the deceleration has been below a predetermined limit value, thetest must be repeated with a brake having a stronger effect.

I claim:
 1. An apparatus for sensing motion parameters of an elevatorthat has at least one cable assembly which is guided over a drivingpulley and has one elevator car suspended therefrom at one end and acounterweight at an opposite end, wherein the elevator car is driven bya drive motor, which acts on the driving pulley, and a braking deviceconnected to the driving pulley, the drive motor and braking devicebeing controlled by a control circuit, the apparatus comprising;anevaluation unit having a timer and a plurality of in-puts connected tothe control circuit, at which control signals are present to selectivelyaccelerate and decelerate the elevator car and the counterweight, afirst position pick-up, connected to one of the in-puts of theevaluation unit in communication with the cable assembly; and a secondposition pick-up, connected to another of the plurality of in-puts ofthe evaluation unit, communicating with the driving pulley; theevaluation unit further including means for determining at leastacceleration values according to distances sensed by the first andsecond position pick-up for checking non-slippage of the at least onecable assembly relative to the driving pulley, the evaluation unitfurther including in-put switches for triggering evaluation processes,including the determination of distances, speeds and accelerations bysignals from the control circuit.
 2. An apparatus as defined in claim 1,wherein said evaluation unit comprises a display device for displayingevaluation results.
 3. An apparatus as defined in claim 2, wherein saiddisplay device is a screen display device.
 4. An apparatus as defined inclaim 2 wherein said evaluation unit comprises a display device forgiving operating instructions to a user of said apparatus.
 5. Anapparatus for sensing parameters of an elevator that has at least onecable assembly which is guided over a driving pulley and bas oneelevator car suspended therefrom at one end and a counterweight at anopposite end, wherein the elevator car is driven by a drive motor, whichacts on the driving pulley, add a braking device connected to thedriving pulley, the drive motor and braking device being controlled by acontrol circuit, the apparatus comprising;an evaluation unit having atimer and in-puts connected to the control circuit, at which controlsignals are present to selectively accelerate or decelerate saidelevator car and counterweight; a first position pick-up, connected toone of the in-puts of the evaluation unit in communication with thecable assembly; and a second position pick-up, connected to another ofthe plurality of in-puts of the evaluation unit in communication withthe driving pulley; said evaluation unit further including means fordetermining at least one of speed and acceleration values according todistances sensed by the first and second position pick-up means forchecking non-slippage of the at least one cable assembly relative tosaid driving pulley; said evaluation unit further including a warningsignal activated in response to predetermined evaluation results.
 6. Anapparatus as defined in claim 5 wherein each said first and secondposition pick-up comprises a perforated disk rotatable in accordancewith the distance to be measured, and at least one light barrier forscanning said perforated disk.
 7. An apparatus as defined in claim 6,wherein said light barrier is a double-type light barrier fordetermining the direction of rotation.
 8. An apparatus as defined inclaim 6, wherein said perforated disk of each first and second pick-upis driven by at least one of a driving roller pressed against saidlifting cable and said driving pulley.
 9. An apparatus as defined inclaim 8, wherein said driving roller comprises a guide groove for acarrying cable of said lifting cable assembly.
 10. An apparatus asdefined in claim 8, wherein said driving roller is plastic.
 11. Anapparatus as defined in claim 1, comprising a force sensing elementremovably arranged between a fixed point and at least one cable of thecable assembly, said force sensing element being connected to an in-putof said evaluation unit.
 12. An apparatus for sensing motion parametersof an elevator that has at least one cable assembly which is guided overa driving pulley and has one elevator car suspended therefrom at one endand a counterweight at an opposite end, wherein the elevator car isdriven by a drive motor, which acts on the driving pulley, and a brakingdevice connected to the driving pulley, the drive motor and brakingdevice being controlled by a control circuit, the apparatuscomprising;an evaluation unit having a timer and in-puts connected tothe control circuit, at which control signals are present to selectivelyaccelerate or decelerate said elevator car and counterweight; a firstposition pick-up connected to one of the in-puts of the evaluation unitin communication with the cable assembly; a second position pick-upconnected to one of the in-puts of the evaluation unit communicatingwith the driving pulley; said evaluation unit further including meansfor determining at least acceleration values according to distancessensed by the first and second position pick-up for checkingnon-slippage of said at least one cable assembly relative to the drivingpulley, and a force sensing element removably arranged between a fixedpoint and at least one cable of the cable assembly, said force sensingelement being a spring-type sensing element connected to one of thein-puts of said evaluation unit.
 13. An apparatus as defined in claim12, wherein said spring-type sensing element comprises at least one of aguided spiral spring and a disk spring.
 14. An apparatus as defined inclaim 12, wherein the spring-type sensing element has a spring excursionand a change in spring excursion can be sensed by a corresponding one ofthe first and second position pick-ups.
 15. An apparatus as defined inclaim 14, wherein each said first and second position pick-up comprisesa coding strip provided with regularly arranged light transmissionwindows for scanning by at least one light barrier.
 16. An apparatus asdefined in claim 15, wherein said coding strip is a sheet metal stripwith regularly spaced holes.
 17. An apparatus as defined in claim 15,further comprising a double-type light barrier, and wherein said codingstrip is scanned by said double-type light barrier.
 18. An apparatus asdefined in claim 14, wherein each said first and second position pick-upcomprises in the alternative a perforated disk or dial gauge rotatablein accordance with a change in spring excursion and a double-type lightbarrier for scanning said disk or dial gauge.
 19. An apparatus asdefined in claim 1, wherein said evaluation unit includes a personalcomputer.
 20. An apparatus as defined in claim 19, wherein saidevaluation unit comprises an interface module arranged upstream in thedirection of signal flow of an input/output interface of said personalcomputer and used for preprocessing the signals of the control means andthe measuring signals of each said first and second position pick-up andof said force sensing element, respectively.
 21. An apparatus as definedin claim 20 wherein said interface module comprises a logic circuit fordetermining at least one of the direction of movement of said elevatorand the direction of spring excursion.
 22. An apparatus as defined inclaim 20, wherein said interface module contains an acoustic transducer.23. A method of sensing motion parameters of an elevator having at leastone cable assembly passed over a driving pulley, the at least one cableassembly having at one end a suspended elevator car and at another end acounterweight, said driving pulley being driven by a drive motorcontrolled by an electric control circuit, and connected to a brakingdevice controlled by the control circuit, wherein said at least onecable assembly, said elevator car and said counterweight are selectivelyaccelerated or decelerated for checking the non-slippage of at least oneof the cable assembly relative to said driving pulley during normaltravel of said elevator, with the motion parameters of said at least onecable assembly and said driving pulley being separately sensed dependingupon time and compared with a given motion limit parameter, sufficientnon-slippage of the at least one cable assembly relative to said drivingpulley, for operating said elevator, being attained when the limitparameter is exceeded.
 24. A method as defined in claim 23, wherein thenon-slippage of the at least one cable assembly relative to said drivingpulley is determined on the basis of the measured difference betweenmotion parameters of said at least one cable assembly and said drivingpulley.
 25. An apparatus for sensing motion parameters of an elevatorthat has at least one cable assembly which is guided over a drivingpulley and has one elevator car suspended therefrom at one end and acounterweight at an opposite end, wherein the elevator car is driven bya drive motor, which acts on the driving pulley, and a braking deviceconnected to the driving pulley, the drive motor and braking devicebeing controlled by a control circuit, the apparatus comprising;anevaluation unit having a timer and in-puts connected to the controlcircuit, at which control signals are present to selectively accelerateor decelerate said elevator car and counterweight, a first positionpick-up, connected to one of the in-puts of the evaluation unit, incommunication with the cable assembly; a second position pick-upconnected to another of the inputs of the evaluation unit incommunication with the driving pulley; said evaluation unit furtherincluding means for determining at least acceleration values accordingto distances sensed by the first and second position pick-ups forchecking non-slippage of the at least one cable assembly relative to thedriving pulley; and a force sensing element removably arranged between afixed point and at least one cable of the cable assembly, to checknon-slippage of the cable assembly relative to said driving pulley,displacement of said cable assembly relative to said driving pulleybeing detected by said first and second position pick-ups, said forcesensing element being connected to one of the plurality of in-puts ofsaid evaluation unit.